"The more I put my foot down...she'd attack me," Chrisoula Workman told a judge when her elder daughter petitioned to become "Modern Family" star's guardian.

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Ariel Winter's sister came out firing against their mom when she moved to become the "Modern Family" star's temporary guardian last month.

"She has been a terror on the set of 'Modern Family,'" Shanelle Gray's attorney, Michael Kretzmer, told a judge Oct. 3, the day Gray filed her motion to remove Ariel from mother Chrisoula Workman's custody. "The producer and others there have expressed grave concern." (ABC has not commented on Ariel's off-camera family drama.)

Gray said, according to a court transcript obtained by E! News, that Ariel had complained about her mother's abusive behavior to her, to her tutor, to their father, "to anybody that will listen, and my father won't help."

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Workman has denied abusing Ariel in any way, stating in her own court filing rebutting Gray's claims that her 14-year-old was rebelling and that Gray, her elder daughter, had just popped back into Ariel's life to take advantage of her success in Hollywood.

Ariel was on the "Modern Family" set with her mother at the time of this hearing, during which Kretzmer expressed concern over what would happen if his client showed up to get Ariel and bring her to court.

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If Workman is on set and is "keeping a tight rein" on Ariel, "if she sees the child leave with her older sister, with whom she's not really interacting too much, that's obviously going to be a red flag and she's going to start putting up obstacles and barriers right there and then," Kretzmer told the judge.

Workman later told E! News that she was blindsided by Gray's court filing.

Glenn Sabey, a private security agent contracted by Gray to serve their mother with the subpoena, told the judge that Workman seemed " a little confused."

Ariel was brought to the courtroom that afternoon, but once Workman arrived, the actress waited out the proceedings in an adjacent conference room while her attorney spoke on her behalf "in light of her expressed and demonstrated nervousness and anxiety," said her lawyer, Amir Pichvai.

Workman told the judge that she had caught Ariel in bed with her then-18-year-old boyfriend, Cameron Palatas, the week before. "I threw him out and I broke them up. And ever since I did that, I've paid," she said. "And, you know, I had to do it."

"She's been seeing him five months" and, after the second month, "I started noticing a change in her," Workman continued. "And then his mother started sending her Bible messages. And his family, she started going over there and going to church with them. And it just started getting too weird for me."

"The more I put my foot down and not let her go party with his friends, she'd attack me," Workman said. "And this last week, I knew something was going on but I didn't know what. She was hitting me, calling me dirty names...She was telling me she was going to make me pay, and she has. She made me pay. And not only that, my little girl is beautiful, smart and talented, and she's going to mess up her life right now."

Ariel and Cameron, 19, have since broken up. A hearing on Gray's petition to become Ariel's permanent guardian is scheduled for Nov. 20.